Goodwill - Goodwill by segment (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016	[2]
Goodwill [Line Items]
Goodwill	$ 770.2	[1]	$ 754.1
Rail Group
Goodwill [Line Items]
Goodwill	134.6		134.6
Construction Products Group
Goodwill [Line Items]
Goodwill	125.8		111.0
Energy Equipment Group
Goodwill [Line Items]
Goodwill	508.0		506.7
Railcar Leasing and Management Services Group
Goodwill [Line Items]
Goodwill	$ 1.8		$ 1.8

[1] (unaudited)

[2] (as reported)